function IsCrackTip

convhull(x,y)
for iCrack=1:nCrack
    CurrCrack=Crack(iCrack);
    xCrack=CurrCrack.x;
    yCrack=CurrCrack.y;
    xTip=xCrack([1,end]);
    yTip=yCrack([1,end]);
    for iTip=1:2
        [xTip(iTip),yTip(iTip)]
    end
end